Valve mechanism for air compressors



Nov. 11, 1941. L. D. HARRISON 2,252,396

VALVE MECHANISM FOR AIR COMPRESSORS Filed Aug. 19, 1938 2 Sheets-Sheet 2 INVENTOR.

ii wz MMKZM ATTORNEY Patented, Nov. 11, 1941 VALVE MECHANISM FOR AIR COMPRESSORS Laurence D. Harrison, Pho enix, Ariz. Application August 19, 1938, Serial No. 225,766

19 Claims.

My invention relates to valve mechanism for air compressors, particularly those of the high speed type, and has for its objects:

First, the provision of a mechanism whereby the exhaust valve operates automatically when the receiver tank pressure is being built up from zero to a predetermined pressure somewhat less than the working pressure, whereby economy of, operation is effected sinceit is unnecessary to use power to compress thecharge within the cylinder to full working pressure before the point of opening of the exhaust valve is reached and thereafter permits it to expand into the receiver.

lifter whereby the time of opening of the exhaust valve .may be 'quickly and easily changed, ad-

justed and set, without changing the point of closing, so that the compressor may be adjusted to [economically operate at different receiver pressures. V

,A third object is to provide a means for adjusting the time of opening of the intake valve without changing the time of its closing, whereby the intake valve opens only after theair in the clearance space above the piston, has expanded on the'do-wnward stroketo atmospheric or intake pressure. By reason of this, the power of the air compressed in this clearance space is utilized on the downward stroke, which would be otherwise lost if the intake valve were permitted to open immediately at the start ;of the downward stroke. j

\A fourth object is to provide a novel type of valve stem packing adaptable to thetype of exhaust valve herein disclosed.

And, a fifth object is to provide a construction of related parts, combined with said above mentioned mechanism whereby either orboth the exhaust orintakevalve may be rendered inoperative; The former by disengaging the valve operating mechanism whereby thevalve remains closed, and the latter by disengaging the valve operating mechanism whereby the valve remains continuously open.

Other objects will appear hereinafter.

I attain the foregoing objects by means of the mechanism construction and devices illustrated in the accompanying drawings, in which;

Figure 1 is a plan view of an air compressor head, showingone set of valves as mounted on said cylinder head, operative on one cylinder of a multi-cylinder compressor;

Figure 2 is a cross section thereof, taken substantially on lines 2-2, Fig. 1;

Figure 3 is a cross section thereof taken substantially on lines 3-3, Fig. l;

Figure 4 is a front elevation thereof;

Figure 5 is a plan view of my improved cam lifter;

Figure 6 is a section thereof taken substantially on lines 6-6, Fig. 5;

Figure 7 is a cross section thereof stantially on lines ,1-l, Fig. 5;

Figure 8 is a side elevation of said cam lifter shown in relative position to the intake valve cam;

Figure 9 is a perspective view of a rocker arm disconnector; and,

Figure 10 is a fragmentary section of the exhaust valve showing a modified form of valve stem sealing means.

Similar numerals refer to the similar parts in the several views.

In the cylinder head assembly, Figures 1, 2, 3 and 4, reference numeral 2 indicates the cylinder, 3 the cylinder block, and 4 a fragment of the cylinder head block, so far as is necessary to illustrate the valve mechanism operative thereon. Attached to this cylinder head are two supports 5 and 6, provided with bearings and adapted to support the camshaft I along and above the outer right hand edge of the head casting, as well as the rocker arm shaft 8, which is posie. tioned above and inwardly from the cam shaft.

As herewith illustrated, it is to be understood that the cam shaft is of the overhead type, receiving its proper operative motion through link chain or gear mechanism from the crank shaft taken suband operative at crank shaft speed in the direction indicated by the arrows; that is, a counterclockwise direction as viewed in Figure 2. This cam shaft carries two sets of cams, the exhaust cam S end the intake cam ID. The former is provided with a small anti-friction roller l I, but the latter, being designed to hold the intake valve open for a longer period of rotation, is preferably of the solid type, as illustrated in Figure 8. These cams operate cam lifters l2 and [3 respectively, by contacting the arcuate under surface [4 of the cam lifter body. The inner end of each cam lifter is supported and journalled upon the rocker arm shaft 8, which is stationary.

a 23 at its outer end to receive an operative lever.

This eccentrically mounted thimble with its operative lever is termed a valve disconnector.

The inner end of the exhaust valve rocker arm terminates in a contact ball 25 adapted to operate on the upper end of valve stem 26 to open the valve by downward pressure in the usual manner. In a similar manner the inner end of the intake valve rocker arm I6 terminates in a contact ball 28 and operates on the upper end of intake valve stem 29 in the usual manner.

The exhaust valve 30, is seated in the exhaust port 3| in such a manner as to be outwardly opening from the compression space 32 in the top of cylinder 2. When opened, air is released into a manifold 33, made a part of head casting 4 and running throughout the length of the cylinder block on which the mechanism is incorporated. This design permits a construction with 1 a minimum of head compression space. The lower portion of valve stem 26, designated by numeral 34, has a larger diameter than the upper portion and terminates in a shoulder 35. Just above this shoulder a threaded portion is provided to receive lock nuts 36, which may be forced down airtight on the upper end of a cylindrical accordion seal 61. The lower end of this accordion is held airtight within the annular recess 38 in head 4 by a sealing ring 39. Thus constructed the valve stem is positively sealed in airtight relation to head 4, although its opening and closing motion is adequately permitted by reason of the accordion seal 31.

Surrounding said sealing means is an annular cup 40, to which two accordion expansion cylinders 4| and 42 are welded. The upper edges of these cylinders are each Welded to the lower spring cup 43. This construction provides an annular vertically expansible chamber 48 be tween the head casting andthe spring seat. A tube 44 opens into this chamber and is adapted to be connected to the compressed air receiver. Exhaust valve spring 45 extends from the lower spring cup 43 to the upper spring cup 46 where it is lockedonto the valve stem by split ring 41 in the usual manner. The tension spring 45 is such that the exhaust valve is barely held shut when the expansible chamber 48 is fully collapsed due to the absence of pressure within it. Further, the material of spring 45 is of such dimension and temper that when the expansible chamber 48 is fully extended (as illustrated in Fig. 2), air compressed in cylinder 2 will not open exhaust valve 30 without the mechanical aid of rocker arm I5.

Since it is desirable, in order to accomplish the objects hereinabove set forth, to regulate the point of opening of the exhaust valve relative to the upward compression stroke of the piston, I provide the adjustable cam lifters I2 and I3. Both intake and exhaust cam lifters are the same. Both are supported and journalled on rocker arm shaft 8. These cam lifters consist of an inner part 56, which is provided with the journal 5| to bear upon shaft 8, and the outer part 52 which includes the arcuate cam bearing surface I4 on its under side. These parts are radially adjustable from the axis of the rocker arm shaft by means of the left and right hand screw 53, held in place by lock nut 54. These two parts are maintained in alignment by the dovetailed sectional construction shown in Figure '7. Part 50 has a semicircular recess 55 to receive push rod ball II. Part 52 is proportioned so that the cam lifter bearing surface I4 is set with the center of its generating radius outwardly eccentric to the axis of cam shaft I. These parts are relatively set and positioned so that as the cam roller I'I contacts the surface I4 of the lifter I2, a position is reached where the cam roller II raises lifter I2 prior to the point of lift if it were governed only by the horizontal portion 56 of the cam lifter surface. The point of commencement of lift can be varied by adjusting the radial position of part 52 relative to part 50. Thus, if part 52 is adjusted to benearer the axis of shaft 8, the cam roller H engages the arcuate portion I4 of the cam lifter sooner and effects an earlier opening of valve 30.

The same construction produces a similar operative result with reference to intake valve cam I0 operative on intake valve cam lifter I3.

In both instances it will be noted that the time of closing of the valves isv not disturbed by changing the point of opening, since the valve closes after the cam has passed the flat portion 56 of the lifter face.

The intake valve 60 is of usual construction, being held closed by spring 61 operative on stem 62. It is seated in a recess 63 in the top of cylinder 2 to permit a maximum movement of the piston and a minimum volume of head space. The intake port is designated by numeral 64.

In order to render the compressor inoperative as when suificient pressure. has been built up in the receiver, I provide throw out mechanism or valve rocker arm disconnecting means, which includes the eccentrically mounted rocker arm bearing thimbles 20, heretofore described. Movement of the lever 2.2 from the position indicated by solid line to the position indicated by dotted lines, tends to raise the axis of rotation of cam lifter I5 to a point where the contact ball 25 no longer operates the top of valve stem 26. When this is done coil spring I9 surrounding thimble 20 forces exhaust valve rocker arm I5 to ride entirely on cam lifter I2. Conversely, rocker arm I6 may be depressed by a similar motion of the thimble on which it bears and the intake valve held open. By operating these levers in unison the entire compressing operation may thus be stopped by holding open the intake valve and not opening the exhaust valve. If operated singly the air compressing may be controlled as desired.

In the construction of devices when air pressures used do not make it feasible to provide the accordion seal 35 for the exhaust valve 30, as illustrated in Figure 2, I have provided the alternative structure shown in Figure 10. Here the I exhaust valve 30 is provided with a stem having an enlarged lower portion I0 and a smaller upper portion II. A plurality of grooves I2 are cut in the stem portion I0 and fitted with tightly fitting compression rings I3, which are ground and sized similar to metallic piston rings. A duct I4 connects the area of the valve stem guide I5 adjacent these rings with a pipe I6 adapted to supply oil under a slightly greater pressure than the receiver air pressure. This valve stem provided with these rings operating in the valve stem guide and supplied with oil under pressure, as stated, forms an effective means of preventing leakage around the valve stem, and under certain operative conditions, is the mechanical equivalent of the sealing means first above described.

An air compressor provided with a piston head and valve mechanism, as herewith illustrated, may be operated in far greater speeds than those now in common use for the reason that both valves are mechanically operated and there is no lag due to inertia common with automatic or flutter valves. When so constructed and operated, economy of power consumption is efa few pounds above working pressure, as is ordinarily done, and then releasing it to expand into the lower pressure in the receiver. On the contrary, as soon as pressure in the cylinder reaches a point a, few pounds above that in the receiver, exhaust valve 30 opens and acts as an automatic, valve, due to the fact that the spring 45 has not been placed underfull tension.

After tank pressure has been reached, operative economy, so far as power consumption is concerned, is attained by reason of the adjustability of the cam lifters l2 and 13. Where it is desired to maintain a definite working pressure in the receiver the intake cam lifter is adjusted by means of its screw 53 so that the intake valve opens on the downward stroke just after the residual air, or air previously compressed in the clearance space above the top of the piston at the top of the cylinder has reached atmospheric or intake pressure. It is well known that this residual air has a cushioning effect on the operation of compressors and to permit this air to escape back into the intake port permits a loss of power stored in this volume of compressed air. On the downward stroke, however, as soon as this residual air has reached atmospheric pressure, it is necessary to quickly open the intake valve before a vacuum is pulled. Therefore, the point of opening of the intake valve is critical and depends on the pressure of the residual head space air. This, in turn, is governed by the working pressure in the receiver. Therefore, where different pressures are desired in the receiver due to any-change of compressed air tools, or uses to which the air is put, the point of opening of the intake valve may be readily changed to effect the economy desired, and by the construction and design of this type of cam lifter the point of opening quickly changed to suit the different conditions.

At the same time, the point of closing of the intake valve will remain constant since it is desirable that regardless of the point of opening, the intake valve should remain open until the bottom of the stroke is reached.

In the case of the exhaust valve, economy is also effected by adjusting the point of opening to correspond to the pressure to be maintained in the receiver. The exhaust valve should open onlywhen the pressure in the cylinder head is a few pounds greater than that in the receiver. If the exhaust valve opens before this point is reached then air rushes from the receiver back into the piston and the driving mechanism is compelled to exert energy to overcome this back pressure throughout a greater portion of the cycle than it otherwise should; further, this pressure must be overcome during a portion of the upper quadrant of the crank cycle where the crank pin is at a more disadvantageous angle than it is when the top of the stroke is approached. Should the mechanically operated exhaust valve open too late; that is, after the pressure in the top of the cylinder has exceeded that in the receiver, then there is loss of power due to the fact that this pressure is needlessly built up in the cylinder, only to be released again into the lower pressure of the receiver. Therefore, it is obvious that the point of opening of the exhaust valve is critical for any given operative pressure in the receiver. By means ofthe cam adjustment herein disclosed this critical point of valve opening can be easily adjusted to suit the conditions desired and consequent economy effected.

I claim:

1.-In valve mechanism for air compressors having poppet valves provided with valve stems with outwardly extending heads, a valve lifter, adapted to receive motion, from a valve cam and transmit it to the valve stem head, having means for adjusting the time of opening of said valve independently of the time of closing thereof, comprising a body having a cam contacting surface with a flat rear portion and a forward leading portion extending arcuately downward, substantially conforming to the circle of cam travel, together with means for adjusting the point of primary contact of the cam with said arcuate surface.

2. In valve mechanism for air compressors a valve lifter adapted to receive motion from a valve cam and transmit same to valve operating mechanism including a body composed of two portions, the inner portion being adapted to be swingably supported on a shaft axially parallel to the cam shaft, the outer portionhaving a cam contacting surface with a flat after portion adjoining a leading portion arcuately depending therefrom, forming a quadrant substantially con-.- forming to the arc of cam travel, and means intermediate said body portions to adjust the distance between the axis of support and said arcuate cam contacting surface.

3. In valve mechanism for air compressors, a poppet exhaust valve, operative in a cylinder head, provided with an helical valve spring, an expansible pneumatic chamber intermediate said valve spring base and said cylinder head adapted to regulate said valve spring tension relatively according to pneumatic pressure supplied to said expansible chamber, and means for supplying pneumatic pressure to said expansible chamber.

4. Valve mechanism for air compressors, including a cylinder head, intake and exhaust valve ports therein provided with seats and valve stem guides for poppet valves, a compressed air receiver connected to said exhaust valve port, a poppet intake valve operative in said intake port, an outwardly opening poppet exhaust valve operating in said exhaust port, mechanical mechanism for opening said valves, including a cam shaft mounted and journalled on said cylinder head, cams operative thereon, valve lifters operatively bearing on said cams, and rocker arms operative intermediate said valve lifters and said valve stem heads mounted on a rocker arm shaft, parallel and centrally positioned relative to said cam shaft, a stationary rocker arm shaft, said valve lifter being journaled on said rocker arm shaft and extending over said cams respectively, so that their under surfaces form cam contacting surfaces, said cam contacting surfaces having a flat rear portion and an arcuately depending forward portion forming a quadrant extending toward the direction of cam rotation with a radius substantially the same as that of the cam rotation, said cam lifters having means whereby the said cam contacting surface is radially ad- .iustable relative to the axis of said rocker arm shaft on which they are mounted.

5. Valve mechanism for air compressors, including a cylinder head, intake and exhaust valve ports therein provided with seats and valve stem guides for poppet valves, a compressed air receiver connected to said exhaust valve port, a poppet intake valve operative in said intake port,

an outwardly opening poppet exhaust valve operating in said exhaust port, mechanical mechanism for opening said valves, including a cam shaft mounted and journalled on said cylinder head, cams operative thereon, valve lifters operatively bearing on said cams, and rocker arms operative intermediate said valve lifters and said valve stem heads mounted on a rocker arm shaft, parallel and centrally positioned relative to said cam shaft, a stationary rocker arm shaft, said valve lifters being journaled on said rocker arm shaft and extending over said cams respectively, so that their under surfaces form cam contacting surfaces; said cam contacting surfaces having a flat rear portion and an arcuately depending forward portion forming a quadrant extending toward the direction of cam rotation with a radius substantially the same as that of the cam rotation; said cam lifters having means whereby the said cam contacting surface is radially ad- J'ustable relative to the axis of said rocker arm shaft on which they are mounted; said exhaust valve having a spring with a tension normally permitting it to open automatically and independently of the action of said exhaust valve opening mechanism and an expansible pneumatic chamber positioned intermediate said exhaust valve spring and said cylinder head, adapted to pneumatic connection to said air compressor receiver, whereby said exhaust valve spring is compressed relatively to the pressure contained in said receiver.

6. Valve mechanism for air compressors as described in claim 5 in combination with disconnecting mechanism for rendering said valves inoperative, including thimbles forming journals for said rocker arms eccentrically mounted on said rocker arm shaft having outwardly extending operative levers, and means intermediate said exhaust valve stem and said head casting forming a pneumatic seal and permitting the normal functioning of said valve.

7. In valve operating mechanism for air compressors, the combination of a cam shaft, a cam body thereon carrying an anti-friction roller to form the cam lobe, and a cam lifter operatively associated therewith, said cam lifter having a flat contacting surface at the termination of the lift and an adjoining arcuately downwardly depending surface at the commencement of the lift.

8. A valve mechanism for air compressors, as described in claim 5, in combination with disconnecting mechanism for rendering said valves inoperative including thimbles forming journals for said rocker arms eccentrically mounted on said rocker arm shaft having outwardly extending operating levers and positioned so that rotary movement of said thimbles will move said rocker arms from operative to inoperative position relative to said valves.

9. In valve stem mechanism for air compressors, as a sub-combination, throw out mechanism to render valves inoperative comprising a rocker arm adapted to communicate motion from a cam lifter to a valve stem head, a poppet valve having a stem, a cam lifter, a thimble on which said rocker arm is journalled having an outwardly extending operating lever, a stationary rocker arm shaft, said thimble being eccentrical- Fly journalled on said rocker arm shaft whereby rotation of said thimble will move said rocker arm from operative to inoperative position.

10. In valve mechanism for air compressors, as a sub-combination, an adjustable valve lifter adapted to adjust the time of valve opening without altering the time of closing, comprising, in combination with a rotary cam and a stationary supporting shaft, a valve lifter body composed of an inner part and an outer part, said inner part being hingedly journalled on said supporting shaft, said outer part having a cam contacting surface positioned to operatively contact said rotary cam, said cam contacting surface including an arcuate surface at the commencement of the lift adjacent a flat surface at the termination of the lift, said outer portion containing said arcuately contacting surface being radially adjustable relative to the axis of said supporting shaft.

11. Valve mechanism for air compressors, including a cylinder head, intake and exhaust valve ports therein provided with seats and valve stem guides for poppet valves, a compressed air receiver connected to said exhaust valve port, a poppet intake valve operative in said intake port, an outwardly opening poppet exhaust valve operating in said exhaust port, mechanical mechanism for opening said valves, including a cam shaft mounted and journalled on said cylinder head, cams operative thereon, valve lifters operatively bearing on said cams, and rocker arms operative intermediate said valve lifters and said valve stem heads mounted on a rocker arm shaft, parallel and centrally positioned relative to said cam shaft, a stationary rocker arm shaft, said valve lifter being journaled on said rocker arm shaft and extending over said cams respectively, so that their under surfaces form cam contacting surfaces, said cam contacting surfaces having a fiat rear portion and an arcuately depending forward portion forming a quadrant extending toward the direction of cam rotation with a radius substantially the same as that of the cam rotation, said cam lifters having means whereby the said cam contacting surface is radially adjustable relative to the axis of said rocker arm shaft on which they are mounted; said exhaust valve having a spring with a tension normally permitting it to open automatically and independently of the action of said exhaust valve opening mechanism and an expansible pneumatic chamber positioned intermediate said exhaust valve spring and said cylinder head, adapted to pneumatic connection to said air compressor receiver, whereby said exhaust valve spring is compressed relatively to the pressure contained in said receiver, and means intermediate said exhaust valve stem and said head casting forming a seal therebetween and permitting the normal functioning of said valve.

12. Valve mechanism for air compressors including a poppet valve having a stem, a valve seat included in a head casting, a spring operative on said stem normally holding said valve closed, sealing means to prevent escape of air between said head casting and said valve stem and permit free movement of said valve, including a longituclinally expansible cylinder surrounding said valve stem attached at one end to said valve stem and to said casting at the other end, mechanism for mechanically operating said valve so that the point of valve opening may be varied independently of the point of closing, including a cam, a valve lifter operated thereby and mechanism for communicating motion from said valve lifter to said valve stem, said valve lifter having a fiat cam contacting surface adjoininga curved cam contacting surface positioned at the place of primary cam contact, and mechanism for varying the point of primary contact of said cam upon the curved cam contacting surface of said valve lifter.

13. In an air compressor, as herein disclosed, as a sub-combination, valve mechanism including an outwardly opening poppet valve having a stem, a head casting having a valve seat, valve stem guide and air port, mechanical mechanism for operating said valve including a guide and a valve lifter, a valve spring normally closing said valve with a tension so that it will open automatically by differential air pressure independent of said mechanical mechanism, and means for regulating said valve spring pressure'including an exp'ansible member operative between said valve springv base and said head casting.

14. In an air compressor,valve mechanism including a poppet valve having a stem, a head casting having a valve seat and valve stem guide and ports, a spring operative on said valve stem, and mechanical mechanism including a cam and valve lifter for operating said valve, mechanism intermediate said valve stem and said operative mechanism for adjusting the point of opening of said valve, including a cam having a lug, a valve lifter swingably supported adjacent said cam having a flat cam contacting surface joining a curved cam contacting surface extending arcuately substantially conformable to the circle of cam lug travel, means for varying the distance from the point of support of said valve lifter to said curved cam contacting surface whereby the point of primary contact of said cam lug with said valve lifter can be varied to change the time of opening of said valve.

15. In an air compressor, as herein disclosed, as a sub-combination, valve mechanism including an outwardly opening poppet exhaust valve having a stem, a cylinder head casting having a valve seat and air port, mechanical mechanism for the opening and closing of said valve, a helical valve spring surrounding said valve stem and operatively attached thereto near the outer end of said valve stem, together with sealing means to prevent escape of air around the said valve stem, including a valve stem guide and oil grooves and packing rings on said valve stem, and means for supplying oil under pressure thereto, a longitudinal expansible cylinder operative within predetermined limits intermediate said valve spring base and said casting, adapted to receive internal pressure and expand therefrom against said valve spring base exerting pressure thereon, and adapttraction thereof, and means for supplying pressure to the interior of said longitudinal expansible cylinder.

16. In an air compressor, as herein described, as a sub-combination, valve mechanism including a compressor cylinder, a casting having a valveseat, valve stem guide and airport, mechanical mechanism for opening and closing an outlet valve at predetermined intervals, together with, a poppet outlet valve having a stem and closing on said seat, a helical valve spring surrounding said valve stem and operatively attached near the outer end thereof, a longitudinal expansible cylinder intermediate the said valve spring base and the said casting, adapted to expand with the introduction of pressure to the interior thereof and to contract within predetermined limits when the total force of the air pressureexerted on the interior face of the said outlet valve exceeds the pressure on the exterior face of said valve together with the pressure exerted on the said valve spring base from the interior of said longitudinal expansible cylinder, and means for supplying pressure to the interior of said longitudinal expansible cylinder.

17. In an air compressor, as herein disclosed, as a sub-combination, valve mechanism including an outwardly opening one piece poppet exhaust valve having a stem operatively attached to a helical valve spring surrounding said valve stem and normally holding said valve in a closed position, a head casting having a valve seat and air port, mechanical mechanism for opening and closing said valve at predetermined intervals, a valve stem guide, means for supplying oil under pressure to a portion of said valve stem guide surrounding said valve stem, together with means for partial opening of said valve by differential air pressure independent of the mechanical opening thereof.

18. In an air compressor, as herein disclosed, as a sub-combination, valve mechanism including a compressor cylinder, a head casting having a valve seat, valve stem guide and air port, mechanical mechanism for opening and closing of a poppet valve at predetermined intervals, together with, an outwardly opening poppet valve having a stem and operative with said valve seat, said valve guide and said air port, and means whereby said valve partially opens automatically when a predetermined air pressure is reached within the cylinder prior to the time of the mechanical opening of said valve.

19. In an air compressor, as herein disclosed, as a sub-combination, means for automatic part1al opening of a mechanically operated outwardly opening poppet exhaust valve seated in a castmg and normally held closed by a spring, including a longitudinal cylinder operative intermediate said casting and said spring, adapted to expand from fluid pressure supplied therein and contract from pressure exerted by said spring thereon, and means for supplying fluid pressure therein.

1 LAURENCE D. HARRISON. 

